1. Field of the Invention
The present invention relates to a plaster containing felbinac and, more particularly, to an anti-inflammatory, analgesic plaster containing felbinac of an anti-inflammatory, analgesic agent as a medicinally effective component for the purpose of curing lumbago, myalgia, periarthritis, and so on.
2. Related Background Art
Felbinac (4-biphenylacetic acid) is an active metabolite of fenbufen, a non-steroid type anti-inflammatory, analgesic agent, and is a drug demonstrating strong anti-inflammatory and analgesic actions. Since this drug is not suitable for oral administration, the attention has been focused on studies on preparations for dermal administration. Gels, liquids, and poultices containing the above-stated drug are commercially available hitherto. The gels and liquids, however, had problems of difficulty in administration in a given quantity, low bioavailability, adhesion to clothing, a number of administrations (for example, several administrations per day), and so on. The poultices have been developed in order to overcome these problems of the gels and liquids, but they still had problems of incapability of affixing them for a long period of time because of their weak adhesion, low bioavailability, and insufficient persistence of the effect of the drug. Japanese Patent Application Laid-Open Gazette No. Hei. 4-321624 proposed an anti-inflammatory, analgesic plaster in which the chief component of the base was a styrene-isoprene-styrene block copolymer and in which crotamiton was an essential solubilizer.
The inventors, however, found that the anti-inflammatory, analgesic plaster described in the Laid-Open Gazette No. Hei. 4-321624 was not yet satisfactory when felbinac was used as an anti-inflammatory, analgesic agent, as described below. Namely, the anti-inflammatory, analgesic plaster described in above Laid-Open Gazette No. Hei. 4-321624 was not yet satisfactory in that work steps were cumbersome because of the use of crotamiton as a solubilizer for the drug and in that secular decrease in adhesion occurred due to bleeding (percolating to the surface) of crotamiton.
Further, U.S. Pat. No. 5,725,874 proposed a plaster comprising felbinac, a styrene-isoprene-styrene block copolymer, a rosin ester derivative, a plasticizer and polyisobutylene as shown in Examples 36 and 37. However, the plaster disclosed in U.S. Pat. No. 5,725,874 comprised 3-1-menthoxypropane-1,2-diol as an essential solubilizer. The drugs (pharmaceutically effective ingredients including felbinac) in the plaster disclosed in U.S. Pat. No. 5,725,874 existed in fully solubilized or molten state. This was also apparent from the fact that the plasters of Examples 36 and 37 disclosed in U.S. Pat. No. 5,725,874 contained 3-1-menthoxypropane-1,2-diol in an amount of 5.0-7.0 wt % which was larger than that of felbinac (2.0 wt %) The plaster disclosed in U.S. Pat. No. 5,725,874 was not yet satisfactory in that the plaster was insufficient in discharge stability of the drug and in durability of the pharmacological action.
The present invention has been accomplished in view of the problems of the prior art described above and an object of the invention is to provide a plaster containing felbinac that can maintain the adhesion to skin in a high level over a long period of time, that is safe with less irritation of skin, that is excellent in stability of preparations, and that is high in release ability of the drug and excellent in the anti-inflammatory action, thus retaining the effect of the drug for a long period of time.
The inventors conducted extensive and intensive studies to achieve the above object and attained the following knowledge, thus completing the present invention. Specifically, those skilled in the art considered before that, because the drug existed in a crystalline state in the dispersion type plasters containing no solubilizer, percutaneous absorption of the drug must be small to expect the sufficient effect. In spite thereof, the present inventors found that a felbinac-containing plaster containing specific components in a specific composition and having a specific thickness, which is a dispersion type plaster containing no solubilizer and containing felbinac in a semi-solubilized state, had high drug release ability, retained the sufficient, pharmacological action for a long period of time, maintained the adhesion to skin in a high level for a long period of time, and was excellent in stability of preparations and less in the skin irritation, thus accomplishing the present invention.
The felbinac-containing plaster according to the present invention is a plaster comprising a styrene-isoprene-styrene block copolymer 10-40 wt %, a rosin-based resin 5-30 wt %, a plasticizer 20-70 wt %, polyisobutylene 6-40 wt %, an antioxidant 0.1-5 wt %, and felbinac as a medicinally effective component 1.1-10 wt %, wherein said plaster does not contain crotamiton which is a solubilizer for said felbinac, said felbinac is uniformly dispersed in a semi-solubilized state in said plaster, wherein solubilized felbinac and microcrystalline felbinac coexist in said plaster, and a thickness of said plaster is 50-300 xcexcm.
Further, the felbinac-containing plaster according to the present invention preferably consists essentially of a styrene-isoprene-styrene block copolymer 10-40 wt %, a rosin-based resin 5-30 wt %, a plasticizer 20-70 wt %, polyisobutylene 6-40 wt %, an antioxidant 0.1-5 wt %, and felbinac as a medicinally effective component 1.1-10 wt %, wherein said plaster does not contain crotamiton which is a solubilizer for said felbinac, said felbinac is uniformly dispersed in a semi-solubilized state in said plaster, wherein solubilized felbinac and microcrystalline felbinac coexist in said plaster, and a thickness of said plaster is 50-300 xcexcm.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.